The present invention relates to methods and apparatus for exercising a person""s quadriceps muscles in isolated, closed chain fashion.
The quadriceps muscles constitute one of the human body""s major muscle groups, and these muscles are primarily responsible for moving a person""s legs from a bent knee position to a straight leg position. Exercise machines have been built for the specific purpose of resisting this particular motion and thereby strengthening and/or toning the quadriceps muscles.
A conventional quadriceps exercise machine, known in the fitness industry as a leg extension machine, is shown in FIGS. 6-7. The prior art leg extension machine 90 generally includes a frame 91, a seat 92 rigidly mounted on the frame 91, a pivot arm 93 pivotally mounted on the frame 91, and a weight stack resistance device 97 operatively connected to the pivot arm 93. The resistance device 97 includes a variable amount of weight 98 that is connected to the pivot arm 93 by means of a cable 99. The components are preferably arranged so that a user""s knee is axially aligned with the pivot axis of the pivot arm 93, and a pad 94 is mounted on an opposite, distal end of the pivot arm 93 to bear against the user""s shin. Counter-clockwise rotation of the pad 94, caused by straightening of the user""s leg at the knee (but not the hip), is resisted by gravity acting upon the weight 98.
The leg extension machine 90 has been a staple item in fitness clubs for decades. Typically, it is provided as part of a circuit of a dozen or so machines, each of which is dedicated to a single exercise and/or a particular muscle group. In this regard, the leg extension machine 90 is provided for isolated exercise of a person""s quadriceps muscles. Generally speaking, the theory behind these circuits is that each machine allows a person to focus on a specific muscle group or exercise movement, and several people can use alternative machines in parallel. In another familiar arrangement suitable for circuit training, a similar leg extension arrangement is supported by a relatively larger frame that also supports several other types of exercise mechanisms (sometimes referred to as a universal gym).
Unfortunately, recent medical opinions are suggesting that conventional leg extension machines (and mechanisms) may cause pain and/or damage to a person""s knees. One possible explanation is that the conventional leg extension exercise involves an xe2x80x9copen chainxe2x80x9d arrangement, wherein the person""s lower leg is loaded in cantilevered fashion. Generally speaking, this sort of exercise tends to impose significant shearing force on a person""s joint (in this case, the knee). On the other hand, a xe2x80x9cclosed chainxe2x80x9d exercise involves stabilization of the distal ends of any limbs being exercised, thereby contributing to joint stability and coordinated interaction of the associated body components.
One type of conventional xe2x80x9cclosed chainxe2x80x9d exercise machine, known in the fitness industry as a leg press machine, is shown in FIGS. 8-9. Like the leg extension machine 90, the leg press machine 80 has also been a staple item in fitness clubs for decades, and is similarly provided as part of a circuit of machines and on universal gym units. The prior art leg press machine 80 generally includes a frame 81, a seat 82 slidably mounted on the frame 81, a foot platform 83 mounted on the frame 81 in front of the seat 82, and a weight stack resistance device 87 operatively connected to the seat 82. The resistance device 87 includes a variable amount of weight 88 that is connected to the seat 82 by means of a cable 89. Movement of the seat 82 away from the foot platform 83, caused by extension of the user""s legs at both the hip joints and the knee joints, is resisted by gravity acting upon the weight 88. Another common type of leg press machine (not shown) has a fixed seat and a pivoting foot support. Movement of the pedals away from the seat is similarly caused by extension of the user""s leg at both the knees and the hips.
Although conventional leg press machines facilitate closed chain exercise of a person""s quadriceps muscles, a significant amount of the user exerted force is generated by a person""s gluteus muscles (due to extension of the user""s legs at the hips, as well as the knees). As a result, conventional leg press machines are ineffective for isolated exercise of a person""s quadriceps muscles. In other words, a need exists for an exercise apparatus that facilitates isolated, closed chain exercise of a person""s quadriceps muscles.
The present invention provides methods and apparatus for exercising a person""s quadriceps muscles in isolated, closed chain fashion. The present invention may be implemented in various ways and/or described with reference to various embodiments. A preferred embodiment includes a frame designed to rest on a floor surface; a body support that is mounted on the frame and includes at least a back rest; and a foot platform that is mounted on the frame in front of the body support. The body support and the foot platform are configured and arranged to support a person in a rest position with his back against the back rest, his thighs extending generally perpendicular to his torso, his legs bent at the knees, and his feet flat against the foot platform. At least one of the body support and the foot platform is pivotally mounted on the frame in a manner that maintains an orthogonal angle between the person""s thighs and torso as the person straightens his legs at the knees while pressing his feet against the foot platform. Also, a resistance device resists straightening of the person""s legs at the knees by resisting relative rotation between the back rest and the foot platform. As a result, the preferred embodiment isolates the user""s quadriceps muscles in a closed chain arrangement. Many features and/or advantages of the present invention will become apparent from the more detailed description that follows.